The measurement of objects and use of the measurements to manufacture replacement parts substantially identical to the original object has long been a goal of industry. In the field of dentistry and the methods of making dental prostheses, e.g., crowns, plates and replacement teeth, this has especially been the case. In the early prior art, the methods required a multiplicity of steps, many of which required intervention in the mouth of the patient. Not only was the patient required to attend the dental practitioner a relatively large number of times, but also the intervention frequently was painful, especially during the fitting stages.
For example, in forming a dental crown, the operations included the grinding of the tooth to be replaced in order to obtain a truncated stump, the taking of an impression of the stump using an elastomer in order to obtain a mold whose hollow part had a shape that was complementary to that of the stump, the casting of plaster into the mold in order to obtain a reproduction of the stump, the preparation of the crown in wax taking into consideration adjacent and antagonistic teeth (a process that was generally highly subjective and the effect of which required high skill and long years of experience by the practitioner), the positioning of the crown in a coating cylinder, the melting out of the wax, the injection of molten metal to replace the wax, the stripping and polishing of the metal crown, and, the setting of the crown on the stump.
in spite of the fact that these numerous operations were carried out by highly skilled dental practitioners, in many cases the prosthesis was then required to be further modified after the initial formation. Because of the large number of steps that were involved, and the fact that even with mechanical impressions accurate fits could not be ensured, and because the relationship of each prosthesis to the adjacent and antagonistic teeth had to be gauged subjectively by the practitioner, the production of a dental prosthesis rarely could be accomplished without many visits to the practitioner for further modifications. Moreover, despite the numerous fitting visits and modifications, the danger that the finished prosthesis would cause discomfort to the patient remained.
Other disadvantages of the early dental prosthesis methods included the use of metals as the material for many dental prostheses. For example, the metals used had to be fluid or malleable at easily obtainable temperatures. The numerous steps in preparing and fitting prostheses required the intervention of a laboratory and skilled practitioners at different stages in addition to a dental surgeon. The equipment, including an oven, sand-blasting machine, and inserting equipment, contributed significantly to the cost of producing the prostheses.
Dental material manufacturers often also provide guidance to use their different products to achieve dental restorations of a given appearance. However, this guidance is often limited to theoretical cases with a prescribed appearance matching a finite number of shade guide tabs. The main problem is that natural teeth never perfectly match the shade tabs and translucency is not usually taken into account.
Furthermore, the recipes provided assume that there is a given constant thickness available to layer the different dental material to achieve the desired result. The problem is that this is often not the case.
The basic laws of physics modeling the interaction of light with matter, including the diffusion of light in translucent material, are well known and documented in the literature. In particular, the Kubelka-Munk model has already been suggested for the use of uniformly layered porcelain. One of the key challenges, however, is the inverse problem; that is given a desired appearance for teeth, how can one recreate it.
Another problem existing in the prior art is in the currently commercially available cosmetic software packages that use images of smiling faces as input and modify these images with standard photo manipulation tools. The dentists use before and after images to sell dental procedures to patients. There is unfortunately no correspondence between software tools and the dental procedures available. The dental procedures may yield results that are not satisfactory to the patient because of the representations the dentist made with the cosmetic software.
Also, whereas U.S. Pat. Nos. 4,611,288, 4,663,720, 4,742,464, 4,952,149, 5,092,022 and 5,237,998 describe devices and methods that measure the shape of teeth and realize dental prosthesis, it is preferable to acquire more information to achieve aesthetic prosthesis. The information needed to achieve improved aesthetic prostheses is the appearance of the desired prosthesis.
An aesthetic smile is based on notion of morphology, symmetry, matched color and translucency, and natural look. There exist various commercially available cosmetic software packages that provide means to modify the shape and alter the color of the teeth. However, no known software is based on precise quantitative data on shape and appearance. The use of finite element analysis and computer simulation in prior art dentistry application is limited to mechanical property concerns.